Of same place



UNITED STATES PATENT OFFICE.

IVILLIAM IV. DEAN, OF ST. LOUIS, MISSOURI, ASSIGNOR TO THE BELLTELEPHONE COMPANY OF MISSOURI, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 573,575, dated December22, 1896.

Application filed June 11, 1896.

To all whom, it may concern.-

Be it known that I, WILLIAM W. DEAN, a citizen of the United States,residing at St. Louis, in the State of Missouri, haveinvented a certainnew and useful Improvement in Telephone-Exchange Systems, (Case No. 11,)of which the following is a full, clear, concise, and exact description,reference being had to the accompanying drawings, forming a part of thisspecification.

My invention relates to telephone-exchange systems in which centralizedbatteries are employed for supplying the transmitter-circuits and itsobjectis to adapt such a centralized battery to systems employinggrounded lines. To this end I employ, in addition to the main battery, abattery in the common return-wire which serves the grounded lines, thisadditional battery being so connected that it cooperates with the mainbattery in supplying the necessary voltage for the grounded lines,leaving the main battery to supply the less voltage, which is usually required for metallic-circuit lines.

My invention consists in the circuits, mechanism, and arrangement ofparts which are hereinafter described, and which will be more readilyunderstood by reference to the accompanying drawings, in which* Figure 1represents two subscribers stations connected together, one subscriberbeing connected with the central station by a metallic circuit, theother by a grounded line. Fig. 2 represents, diagrammatically, the plugsand cord-circuits at the central office.

Like letters refer to similar parts in both figures.

In Fig. 1 the subscribers station S isrepresented with the regularmetallic circuit. When the plug P of the double connectingcord isinserted in the jack J of the subscriber S, current will flow from thebattery 13 by way of the wire e, retardation-coil R to the point p,where it will divide, one part of the current flowing through thewinding d of the induction-coil r to the sheath y of the plug P, to thespring 0, of the jack J, thelimb Z, the contact 0, to thesubscribers-station apparatus, and to the ground. Starting from 1) againthe other part of the current will flow by way of the winding (Z, theclearingout indicator 2 Serial No. 595,109. (No model.)

to the tip a: of the plug P, to the spring a of the jack; thence by wayof the limb Z, the contact 0, the subscribers station, to earth.

It will be seen that battery B supplies the two branches of the metalliccircuit in multiple, and the resistance, therefore, of this circuit ispractically one-half what it would be if only one branch of thecircuitwere used and one-fourth what it would be if the two branches ofthe metallic circuit were in series. It will be seen also thatpractically equal and opposite currrents will flow through the windingsd and (Z, and the core Z of induction-coil I will not be magnetized, sothat the coil will retain its efficiency as a transformer.

The induction-coil I in Fig. l is shown having four layers, two of saidlayers being connected in series and forming one half of theinduction-coil, while the two other layers connected in series form theother half of the induction-coil. In Fig. 2 the induction-coil is shownwith its connections in a simplified diagrammatic form.

Referring to Fig. 1 again, it will be seen that when the plug P isinserted in the jack J of the grounded subscriber S current will flowfrom the battery B, by way of the wires 8 and 6, through coil R to thepoint p, at which point the current will divide, part fiowing throughthewinding (1 by way of the clearing-out indicator '6', to the tip 00 ofthe plug P, to the spring a of the jack by way of the single line 1 thecontact 0 thence by wire 6 the retardation-coil R, to the wire it. Thecurrent here divides, half going through primary circuit k, whichincludes the transmitter t, to the point 0, and the other half flowingthrough the primary winding is and balancing-resistance r to the samepoint 0. Here the current will reunite and flow by way of the commonreturn-line 1, the battery B B to battery 13. Returning to point p itwill be seen that current will also flow through the winding (1 to thesheath y of the plug P, the spring a of the jack J, the non-inductiveresistance T to earth. The resistance r is adjusted so that the samecurrent will flow through the winding (1 as flows through the winding dThere will then be equal and opposite currents flowing through windings(1 and (1?, so that they do not magnetize the core Z of the inductivecoil 1, and its efficiency is maintained the same when used withgrounded lines as when used with metalliccircuit lines. If the spring aof jack J were left in open circuit, then current would flow onlythrough the winding (1 and, as there would be no neutralizing currentflowing through the winding (Z the core Z would be magnetized, and theefficiency of the induction-coil I as a repeating-coil would beimpaired. Still another purpose is secured by the grounding of thespring a of the springjack J through the non-inductive resistance 1' forthereby the alternating voice-currents emanating from the station of thegrounded subscriber S are enabled to pass through the entire inductioncoil I, thus avoiding the weakening of the induction in the coils d andd, which would ensue if winding (1 should be left open at thespring-jack contact y and spring a".

It will be seen that the circuit of the grounded subscriber, in whichthe return-ground 1 is included in series with the single line Z hasmuch greater resistance than a metallic-circuit line in which the twobranches are in multiple when the stations are the same distance fromthe central oiiice. Hence it will be necessary in order to balance thecurrent supplied from the battery to these lines to insert resistancewith the metallic-circuit line to compensate for the extra resistance ofthe grounded-circuit line. This, of course, is objectionable, and this Iavoid by means of my invention.

I will describe the operation of the apparatus and circuits which I havereferred to. Suppose that subscriber S speaks in his transmitter t.Alternating currents will be set up in the secondary circuit .9 and willflow from the grounded battery B B by conductor 1 to the point- 0,thence through the seo ondary helix .9 of the ind uction-coil andhandtelephone T, wire contact 0 line Z spring a plug-contact x,non-inductive resistance 7", and clearing-out indicator 2" in multiple,the winding (1 and the winding (1 upon the repeating-coil I, to thesheath of the plug P, the spring a", the non-inductive resistance T toearth. The battery 13 being inserted in the return-wire 1, supplies nocurrent to the metallic circuit, but is connected in series with batteryB, so that the grounded subscriber has the added voltage of the twobatteries, as will be observed by tracing the circuit of the twobatteries through the station S battery B is connected with the line toearth, the battery supplies the primary circuit ,of the transmitter bythe return-wire 1. Its path is, after leaving the ind uctioncoil,through the retardation-coil B, the line 6 contact 0 line I, spring aplug-tip as, resistance 1", and indicator 2' in multiple, winding (1 tothe point 19 by lines 6 and c to the battery 13, and back to the point10.

Starting from the point w, where the The battery 13 is preferablyprovided of a size sufiicient to supply the additional voltage requiredfor the longest grounded linecircuit over what is required for themetalliccircuit lines and its polarity is opposite to that of thebattery B, as is shown, so that there will be sufiicient voltage tofurnish the grounded subscriber with the standard current. I have shownanother grounded subscriber S connected to a portion of the battery I3indicating that the line Z connecting with station S is of lowerresistance, and therefore will require less of the battery B than thestation S before described. Numerous subscribers may be connected to thecommon returns 1 and 2, it being only necessary to have the differentgroups of grounded lines which are connected to a common return providedwith lines of approximately the same length and resistance, and in thismanner the lines will be furnished with the same stand- 7 ard ofcurrents from the centralized batteries without the necessity ofproviding artificial resistances at the central station, as would benecessary if the battery B were of suflicient electromotive force tosupply the grounded lines having the greatest resist-ance with thestandard of current required.

The retardation-coils R and R are inserted to prevent leakage of voicecurrents to earth through the battery B. The non-inductive resistances1- and 'r are connected in shunt of the clearing-out indicators to forma non-inductive path for the und ulating voicecurrents, which would notpass freely through the electromagnets t' and i.

I believe it is broadly new with me to insert an additional battery ofproper potential in the return-ground, serving a group ofgroun(led-subscribers lines, and I desire to claim this broadly. Ibelieve it is also new with me to put the balancing-resistance r incircuit to ground from the usually open point of a groundedsubscribersspring-jack for the purpose of maintaining the core of therepeating-coil I non ma-gnetic, and this I intend to claim broadly.

It will be apparent that my invention is described in combination withmechanism and circuits which may be modified without departing from thespirit of my invention. I desire, therefore, not to be strictly limitedto the details of mechanism and circuits which I have shown; but,

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is-

1. The combination with metallic-circuit and grounded telephone-lines,of a common battery, and an additional battery in circuit with thegrounded lines and adapted to suping in one spring of a spring-jack, ofa repeating-coil having substantially equal and opposing windingsadapted to be connected in said line, and a balancing-resistance adaptedto be connected between said windings and ground, whereby the efficiencyof the repeatingcoil is increased, substantially as described.

In a telephone-exchange system, the combination with metallic-circuitand grounded telephone-lines, of a common battery adapted to supplycurrent to said grounded telephone-lines and current in multiple to thetwo sides of each of the metallic telephonelines, and an additionalbattery adapted to be included in circuit with said groundedtelephone-lines to reinforce the pressure of said common battery,substantially as described.

at. In a telephone-exchange system, the combination withmetallic-circuit and grounded telephone-lines,of a common batteryadapted to supplycurrent to said lines, and an additional batteryadapted to be included in series with said common battery and in circuitwith said grounded lines, substantially as and for the purposedescribed.

In a telephone-exchange system, the combination with grounded andmetallic-circuit telephone-lines, of a common battery adapted to supplycurrent to said grounded telephone-lines and, in multiple, to the twosides of each of said metallic-circuit lines, and an additional batteryadapted to be included in circuit with said grounded lines and in serieswith said common battery, substantially as and for the purposedescribed.

6. In a telephone-exchange system, the combination with metallic circuitlines grounded at the substation and grounded telephone-lines, of acommon grounded battery adapted to supply current to said groundedtelephone-lines and, in multiple, over the two sides of each of saidmetallic-circuit lines, and an additional battery adapted to be includedin circuit with said grounded telephon e-lines, substantially as and forthe purpose described.

7. .In a telephone-exchange system, the combination withmetallic-circuit and common return telephone-lines, of a common batteryadapted to supply current thereto, and an additional battery adapted tobe included in circuit with said common return, substantially as and forthe purpose described.

8. In a telephone-exchange system, the combination with metallic-circuitand common return telephone-lines, of a common battery adapted to supplycurrent to said common return-lines and, in multiple, over the two sidesof each of said metallic-circuit lines, and an additional batteryadapted to be included in series with said battery and common return,substantially as and for the purpose described.

9. In a telephone-exchange system, the combination with a telephone-lineextending to the exchange, of a repeating-coil, having substantiallyequal and opposing windings, means for connecting one of said windingsin series with said line, means for connecting an opposing winding inshunt of said telephone-line, and balancing-resistance adapted to beincluded in circuit with the latter of said windings, substantially asand for the purpose described.

In witness whereof I hereunto subscribe my name this 29th day of May, A.D. 1896.

WILLIAM W. DEAN. \Vitnesses J. J. ORAWSHAW, F. WoELTGE.

